Data for isolated CABG were retrospectively collected from January 1, 2018 to July 31, 2020, from the Peking University People’s Hospital database. Exclusion criteria :(1) coronary artery disease is unsuitable or unnecessary for BIMA;(2) Combined with subclavian artery stenosis;(3) Preoperative IMA ultrasound indicated that the IMA was fine, narrow or calcified;(4) With concomitant additional procedures. There were 74 patients who underwent CABGs with bilateral internal mammary artery with different configurations we included. According to the different target territories that RIMA grafted to, the patients were divided into bilateral group (group I) with 20 cases and left group (group II) with 54 cases. This study was approved by our institutional Review Board /Ethics Committee. Consent for individual use of data was waived because of the nature of the study and previous approval for the use of such data at the time of operative consent.
All patients underwent CABGs through a median full sternotomy. Stabilization of the target coronary arteries was accomplished with a tissue stabilizer (Octopus, Medtronic Corporation, Minneapolis, MN) and an intra-coronary shunt (Medtronic Corporation, Minneapolis, MN) was used during off-pump CABGs. In on-pump CABGs, cardiopulmonary bypass was established after standard ascending aorta cannulation and 2-stage venous cannulation of the right atrium, all anastomosis were performed after cardiac arrest. 56 cases of LIMA were harvested by pedicled method, and 18 cases were harvested by the skeletonized method. RIMAs were all harvested by the skeletonized method to maximize the length of the internal mammary artery. After systemic heparinization, the distal end of IMAs were cut, which were protected by poppy alkali gauze.
BIMA configurations were as follows:
Group I(20 cases): In situ RIMA to right coronary artery or posterior descending artery with in situ LIMA to left anterior descending artery(Figure 1).
Group II (54 cases) was divided into: (1) In situ RIMA to LAD with in situ LIMA to diagonal branch (D) or left circumflex branch (LCX)(17 cases)(Figure2a).(2)In situ RIMA to D or LCX with in situ LIMA to LAD(14 cases)(Figure 2b).(3)In situ LIMA to LAD and LIMA-Y-free RIMA to D or LCX(13 cases).(4) In situ LIMA to LAD with aorta-free RIMA to D or LCX(10 cases). Other target territories were revascularized by the great saphenous vein or radial artery.
Preoperative internal mammary artery ultrasonography examination
Preoperative blood flow parameters of IMAs were measured by transthoracic doppler ultrasonography machine (APLIO500 TUS-A500, Probe: PLT-704SBT and PVT-712BT). All preoperative internal mammal artery ultrasonography was performed by the same senior ultrasonologist.
Intraoperative transit time flow measurement
The transit time flow of the grafts was measured by The VeriQ system TTFM device (MediStim Inc., Oslo, Norway), equipped with2,3 or 4-mm probes, depending on the size of the graft, under stable haemodynamic conditions without the support of a mechanical device such as cardiopulmonary bypass or an intra-aortic balloon pump. The parameter yielded by TTFM system including(i) the mean graft flow volume (MGF, ml/min), (ii) the pulse index calculated as (PI, maximum flow volume—minimum flow volume)/(mean flow volume) and (iii) the DF, calculated as (flow volume of the diastolic phase)/(flow volume of the systolic phase + flow volume of the diastolic phase). Satisfactory blood flow parameters criteria : 1,ACI＞50%;2,The shape of blood flow waveform is stable and repeatable；3,PI＜5，MGF＞15ml/min. If sufficient graft flow was not obtained, graft revision was considered and performed until diastolic graft flow was confirmed.
Postoperatively, aspirin, nitroglycerine and β- blocker were prescribed on postoperative day 1. The patients were routinely examined by cardiac CT scanning prior to discharge from the hospital unless they had grade 3 or more chronic kidney disease.
The database was established by EpiDate3.1 software, the data were input twice in parallel. The final analysis database is formed after logical error checking and sorting of the input data and analysis and processing of outliers. Continuous variables were expressed as means ±SDs; if the data conformed to a normal distribution, the two groups were compared using an independent samples t test, and multiple groups were compared using variance analysis. For nonnormally distributed data, Wilcoxon rank-sum tests were used for comparisons between two groups, and Kruskal-Wallis H tests were used for comparison between multiple groups. Categorical variables were described as percentages (rates); comparisons between two groups were performed using Pearson’s χ2 test or Fischer’s exact test as appropriate. P<0.05 was considered statistically significant. All analyses were performed in SPSS version 23.